1886-88, Richard F. Burton, The Supplemental Nights to the Thousand Nights and a Night, Night 547:

Now one day of the days,[…]the Sultan cast his eyes upon her as she stood before him, and said to his Grand Wazir, "This be the very woman whereof I spake to thee yesterday, so do thou straightway bring her before me, that I may see what be her suit and fulfil her need."

That can be used to introduce subordinate clauses, but can just as easily be omitted: one can say either “he told me that it’s a good read” (in which case the second clause is a “that clause”) or “he told me it’s a good read” (in which case the second clause is a “bare clause”).

Historically, “that” was usually preceded by a comma (“he told me, that it’s a good read”) — such usage was, for example, recommended by the grammarian Joseph Robertson in his 1785 essay On Punctuation — but this is now generally considered nonstandard.

Historically, that was sometimes used after a preposition to introduce a clause that was the object of the preposition, as in “after that things are set in order here, we’ll follow them” (Shakespeare, 1 Henry VI), which simply means “after things are set in order...” and would be worded thus in modern English.[1]

The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Wiktionary:Entry layout#Translations.

The humor of my proposition appealed more strongly to Miss Trevor than I had looked for, and from that time forward she became her old self again; for, even after she had conquered her love for the Celebrity, the mortification of having been jilted by him remained.

(demonstrative) The thing, person, idea, quality, event, action, or time indicated or understood from context, especially if more remote geographically, temporally or mentally than one designated as "this", or if expressing distinction. [from 9thc.]

To be, or not to be: that is the question: / Whether 'tis nobler in the mind to suffer / The slings and arrows of outrageous fortune, / Or to take arms against a sea of troubles, / And by opposing end them?

1888 July, The Original Secession Magazine, page 766:

[He] was qualified and fitted, both intellectually and morally, — and that to an exceptional extent — to be the Head […]

"I was dragged up at the workhouse school till I was twelve. Then I ran away and sold papers in the streets, and anything else that I could pick up a few coppers by—except steal. I never did that. I always made up my mind I'd be a big man some day, and—I'm glad I didn't steal."

Plastics are energy-rich substances, which is why many of them burn so readily. Any organism that could unlock and use that energy would do well in the Anthropocene. Terrestrial bacteria and fungi which can manage this trick are already familiar to experts in the field.

Some authorities prescribe that that should only be used in restrictive contexts (where the relative clause is part of the identification of the noun phrase) and which or who/whom should be used in non-restrictive contexts; in other words, they prescribe "I like the last song on the album, which John wrote". In practice, both that and which are found in both contexts.[2]

In a restrictive relative clause, that is never used as the object of a preposition unless the preposition occurs at the end of the clause; which is used instead. Hence "this is the car I spoke of" can be rendered as "this is the car that I spoke of" or "this is the car of which I spoke", but not as *"this is the car of that I spoke."

That refers primarily to people or things; which refers primarily to things, and who refers primarily to people. Some authorities insist who/whom be used when making reference to people, but others, such as the Merriam-Webster dictionary, write that such prescriptions are "without foundation" and use of that in such positions is common and "entirely standard".[2] Hence, one sees both "he is the man who invented the telephone" and "he is the man that invented the telephone."

When that (or another relative pronoun, like who or which) is used as the subject of a relative clause, the verb agrees with the antecedent of the pronoun. Thus "The thing that is...", "The things that are...", etc.

In the past, bare that could be used, with the meaning "the thing, person, etc indicated", where modern English requires that which or what. Hence the King James translation of John 3:11 is "We speak that we do know, and testify that we have seen" while the New International Version has "we speak of what we know, and we testify to what we have seen".